Barack Obama quoting Nelson Mandela has become the most liked tweet ever - and scientists agree.

Obama's response to the violence in Charlottesville on Saturday has become the most liked tweet in history. He quoted Nelson Mandela's famous assertion that no one is born racist. As well as being exactly what the world needed, he's also entirely on point according to psychology – scientists have never been able to find such a thing as innate racism.

We might be able to tell the difference between different skin colours as very young children, but this comes with no more values attached to it than noticing someone's hair or eye colour, or the colour of the sky.

"He's right – no one is born racist," psychologist Manos Tsakiris of Royal Holloway University of London told IBTimes UK.

"We are biological organisms, and that means we know how to process fear and anger and threatening events in life. But these are not tied to specific groups in any way. They are formed through experiences in life from social constructions."

How people become racist is an enormous question that psychology alone can't answer. But it can offer insights into facets of the problem.

"We grow up in a society that enforces certain stereotypes because they become dominant through economic and political practice. It's a socially constructed stereotype that black people are seen as a threat," said Tsakiris.

This shapes how our brain processes information about people's race and background. Even for people who do not hold racist beliefs, our brains are primed by social constructions to react unfairly.

"We live in a society where black people are seen as more of a threat. Even for non-racist people this can lead to a response in the brain structure that processes fear, the amygdala."

But this is far from saying that among adults who have grown up in a prejudiced society that racist responses are somehow automatic.

"There might be an initial fear response from the amygdala, but the prefrontal cortex – the part of the brain responsible for conscious thought – tries to control this automatic behaviour of the amygdala. It regulates behaviour so you don't respond with fear," Tsakiris said.

So can psychology provide part of the answer to racism? A recent study found that the hormone oxytocin – which is produced naturally in positive social situations – coupled with role models and examples of tolerance can reduce xenophobic people's prejudice against refugees. Tsakiris' own experiments have shown that giving yourself the illusion of having a different skin colour can also reduce people's implicit racial bias.

In these experiments, people took part in the famous 'rubber hand' illusion, where someone is made to see a fake hand as their own. The participant hides one of their own arms behind a screen and a rubber arm is placed next to them instead. An experimenter then touches or strokes their own hand and the rubber hand simultaneously. The participant can see the rubber hand being touched, but not their own. This gives the peculiar sensation that the rubber hand is your own.

Members of the Rebel Brigade Knights and the Nordic Order Knights hold their torches during a cross-lighting ceremony at a private residence in Henry County, VirginiaJohnny Milano/Reuters

If a white participant did the experiment with a black rubber hand, they had exactly the same experience. The same process of embodiment in a body of a different skin colour is possible through virtual reality. For up to a week after their experiment, the white participants' implicit racial bias was significantly reduced – they no longer had a subconscious fear response, or had a much smaller one, to black people.

"That shows an interesting finding of how we perceive others and ourselves. If you increase your sense of similarity between yourself and others, you can decrease implicit bias," Tsakiris said.

While experiments with rubber hands and VR bodies are by no means going to be a cure for racism, they could play a role in schools and training centres for police officers or people who work with refugees, Tsakiris suggested.

But more broadly, having a greater number of embodied experiences with people of other skin colours is the important thing. This is where psychology meets everything we already know about the dangers of segregation.

"If you have people living in shared communities rather than segregated communities, it's going to help. Sharing life with people from different groups would, I believe, reduce racism," Tsakiris said.

"This increases our sense of psychological similarity between the self and other people. Fundamentally, the more people spend time with different groups from a very early age, the less likely it is they will become racist."

Leo Griffin, 4, leaves a Chicago vigil and protest against the rise of white supremacist movements in the US.Scott Olson/Getty Images